Signatories include former NDP leader Ed Broadbent, former Progressive Conservative minister Flora Macdonald, as well as organizations such as Amnesty International.
Earlier this month, several cabinet ministers lashed out at the special rapporteur, Olivier De Schutter, after his trip across Canada led him to express "extremely severe" concerns about the ability of aboriginal people and families on social assistance to afford the food they need to stay healthy.
In an open letter issued Wednesday, more than 150 organizations and individuals say Ottawa is undermining the authority of the United Nations by publicly attacking its envoys to Canada.
The letter points to personal attacks against De Schutter by Health Minister Leona Aglukkaq, Immigration Minister Jason Kenney and others, in which the ministers said the UN envoy was "ill-informed" and "patronizing", and his mission was "completely ridiculous."
The letter says Canada can't argue for other countries to respect UN human-rights reviews unless it does so, too.
Since her initial comments, Aglukkaq has since said she didn't mean to imply there are no hunger issues in Canada's North, but she resents being getting advice from an outsider who has never been there.
Aglukkaq, from Nunavut, invited De Schutter to come back and go to the North with her to experience the hunting lifestyle there.
De Schutter did meet with First Nations communities in northern Manitoba during his visit. His itinerary was put together by government officials who invited him to Canada, the letter points out.
"Despite all this, Mr. De Schutter has been subjected to unprecedented attacks on his integrity and professionalism simply for having accepted Canada's invitation," it states.
The attack on De Schutter was not the first time the Conservatives have tried to undermine UN experts involved in Canadian policy, the letter adds.
Last year, James Anaya, the UN special rapporteur on indigenous peoples, wrote to say he was concerned about living conditions at the Attawapiskat First Nation in northern Ontario. But Aboriginal Affairs Minister John Duncan dismissed his statements, saying it was a "publicity stunt."
De Schutter's findings and recommendations did not actually present the federal government with radically new information, the letter adds. He reflected findings by parliamentary committees and independent researchers.
If the government wanted to disagree, it should have discussed the findings in a respectful manner, the letter says.
"We expect our government to fully engage with the UN human rights system, recognizing its application to Canada and welcoming the international scrutiny that our signature on human rights treaties rightfully entails," it says.
A spokesman for Foreign Affairs Minister John Baird dismissed the letter, and said the UN has better things to do.
"The UN ranks Canada 6th on its development index," Chris Day said in an email.
"In a world wrought with famine, where too many people go hungry and die of starvation, we think the UN has greater priorities."Suggest a correction